Engine speed control

ABSTRACT

According to one embodiment, an apparatus for controlling operation of an internal combustion engine includes a conditions module that is configured to determine an out-of-gear condition of the internal combustion engine. The apparatus also includes a permission module that is configured to allow a speed of the internal combustion engine to exceed a maximum engine speed limit if the determined out-of-gear condition meets a threshold, and prevent the speed of the internal combustion engine from exceeding the maximum engine speed limit if the determined out-of-gear condition does not meet the threshold.

FIELD

This disclosure relates to the operation of an internal combustionengine, and more particularly to controlling the speed of an internalcombustion engine.

BACKGROUND

The improvement of fuel efficiency or engine brake performance of aninternal combustion engine is a primary concern of engine manufacturers,end users, and regulatory agencies. Many attempts have been aimed atimproving the fuel efficiency of internal combustion engines. However,in many instances, such improvements to the fuel efficiency of an engineoften come at the expense of one or more other performancecharacteristics of the engine. In other words, measures to improve thefuel efficiency of an internal combustion engine may place variousoperational and performance limitations on the engines.

Generally, the amount of fuel consumed by an engine, which is directlyrelated to the fuel efficiency of the engine, is determined based on oneor more predetermined control surfaces. Each control surface includesprecalibrated values for the fuel injection and air handling systems forvarious engine speed and engine load combinations within the operatingrange of the engine. The operating range of the engine is alsopredetermined and is typically referred to as a torque-speed curve. Thetorque-speed curve constrains operation of the engine to a range ofengine speed and engine load combinations. For example, the torque-speedcurve may limit the maximum engine speed or load to improve fuelefficiency, among other reasons. Notwithstanding the potentialimprovements to the fuel efficiency of the engine by instituting speedand load limitations on the engine, other performance characteristicsand/or operations may suffer or be correspondingly limited.

SUMMARY

The subject matter of the present application has been developed inresponse to the present state of the art, and in particular, in responseto the problems and needs in the art that have not yet been fully solvedby currently available controllers or control strategies for internalcombustion engines. Accordingly, the subject matter of the presentapplication has been developed to provide a controller or controlstrategy that overcomes at least some shortcomings of the prior art.More specifically, disclosed herein is an improved control strategy foran internal combustion engine that facilitates improvements in fuelefficiency while allowing an expanded engine high speed range forcertain limited applications, such as, for example, to provide speedsynchronizations with a transmission for downshift events, particularlyduring downhill maneuvers. Such high engine speed during braking eventscan be utilized to provide improved engine braking performance.

According to one embodiment, an apparatus for controlling operation ofan internal combustion engine includes a conditions module that isconfigured to determine an out-of-gear condition of the internalcombustion engine. The apparatus also includes a permission module thatis configured to allow a speed of the internal combustion engine toexceed a governed engine speed if the determined out-of-gear conditionis satisfied (e.g., meets a threshold), and prevent the speed of theinternal combustion engine from exceeding the governed engine speedlimit if the determined out-of-gear condition is not satisfied (e.g.,does not meet the threshold).

In some implementations, the conditions module determines theout-of-gear condition based on engagement of a transmission clutch.According to yet some implementations, the conditions module determinesthe out-of-gear condition based on a difference between the speed of theinternal combustion engine and a speed of a transmission input shaft.Alternatively, the conditions module determines the out-of-gearcondition based on a discrepancy between an expected engine output andtransmission output shaft speed ratio and a detected engine output andtransmission output shaft speed ratio. In yet certain implementations,the conditions module determines the out-of-gear condition based on anelectronic signal from an automated transmission controller.

According to some implementations of the apparatus, the permissionmodule is further configured to allow the speed of the internalcombustion engine to exceed the governed engine speed if the speed ofthe engine is above a downshift speed limit, and to prevent the speed ofthe internal combustion engine from exceeding the governed engine speedif the speed of the engine is below the downshift speed limit. Thedownshift speed limit is less than the governed engine speed.

In certain implementations of the apparatus, the permission module isfurther configured to allow the speed of the internal combustion engineto exceed the governed engine speed if the engine is not operating abovea minimum power threshold, and to prevent the speed of the internalcombustion engine from exceeding the governed engine speed if the engineis operating above the minimum power threshold. The minimum powerthreshold can be equal to the power consumed by accessories powered bythe engine.

According to another embodiment, an internal combustion engine systemincludes an internal combustion engine coupled to a transmission via aclutch. The engine system also includes an engine output shaft (e.g.,crankshaft) and transmission input shaft that can be selectively coupledvia the clutch. Additionally, the engine system includes a controllerthat has a predetermined torque-speed curve that defines a firstoperating region for engine speeds below a governed engine speed and asecond operating region for engine speeds above the governed enginespeed. Fueling to achieve speed operation of the internal combustionengine within the second operating region is allowed only when thetransmission input shaft is selectively decoupled from the engine outputshaft. Once synchronization with the transmission has occurred, theengine may transition into a coasting or braking mode where no fuel isconsumed.

In some implementations, the engine system also includes externalaccessories that are powered by the internal combustion engine.Operation of the internal combustion engine within the second operatingregion is allowed only when the transmission input shaft is selectivelydecoupled from the engine output shaft and when power generated by theinternal combustion engine is not more than the power received by theexternal accessories from the internal combustion engine.

According to some implementations, operation of the internal combustionengine within the second operating region is allowed only when thetransmission input shaft is selectively decoupled from the engine outputshaft during a downshift event. The second operating region may includean upper engine speed limit that is equal to a maximum speed required todownshift out of a top gear when the internal combustion engine isoperating at the governed engine speed.

In yet another embodiment, a method for controlling operation of aninternal combustion engine system includes determining whether theinternal combustion engine system is out-of-gear, providing an engineoperation map comprising a high speed region, allowing access to thehigh speed region when the internal combustion system is out-of-gear,and preventing access to the high speed region when the internalcombustion system is not out-of-gear.

According to some implementations, the method further includesdetermining an engine speed of the internal combustion engine system,allowing access to the high speed region when the engine speed of theinternal combustion engine system is greater than a maximum downshiftspeed, and preventing access to the high speed region when the enginespeed of the internal combustion engine system is less than the maximumdownshift speed. In yet some implementations, the method includesdetermining a power output of the internal combustion engine system,allowing access to the high speed region when the power output of theinternal combustion engine system is not greater than an externalaccessory power consumption, and preventing access to the high speedregion when the power output of the internal combustion engine system ismore than the external accessory power consumption.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the subject matter of the present disclosureshould be or are in any single embodiment. Rather, language referring tothe features and advantages is understood to mean that a specificfeature, advantage, or characteristic described in connection with anembodiment is included in at least one embodiment of the presentdisclosure. Thus, discussion of the features and advantages, and similarlanguage, throughout this specification may, but do not necessarily,refer to the same embodiment.

The described features, structures, advantages, and/or characteristicsof the subject matter of the present disclosure may be combined in anysuitable manner in one or more embodiments and/or implementations. Inthe following description, numerous specific details are provided toimpart a thorough understanding of embodiments of the subject matter ofthe present disclosure. One skilled in the relevant art will recognizethat the subject matter of the present disclosure may be practicedwithout one or more of the specific features, details, components,materials, and/or methods of a particular embodiment or implementation.In other instances, additional features and advantages may be recognizedin certain embodiments and/or implementations that may not be present inall embodiments or implementations. Further, in some instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the subject matter ofthe present disclosure. The features and advantages of the subjectmatter of the present disclosure will become more fully apparent fromthe following description and appended claims, or may be learned by thepractice of the subject matter as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the subject matter may be more readilyunderstood, a more particular description of the subject matter brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the subject matter and arenot therefore to be considered to be limiting of its scope, the subjectmatter will be described and explained with additional specificity anddetail through the use of the drawings, in which:

FIG. 1 is a schematic block diagram of an engine system having aninternal combustion engine and a controller in accordance with onerepresentative embodiment;

FIG. 2 is a schematic block diagram of the controller of FIG. 1 inaccordance with one representative embodiment;

FIG. 3 is a schematic block diagram of an engine command module of thecontroller of FIG. 2 in accordance with one representative embodiment;and

FIG. 4 is a schematic flow chart diagram of one embodiment of a methodfor controlling the operation of an engine system.

DETAILED DESCRIPTION

According to one embodiment depicted in FIG. 1, an internal combustionengine system 10 includes an internal combustion engine 20 powered by afuel. Although not shown, the engine system 10 may be placed within orform part of a vehicle and be configured to operate and propel thevehicle. The engine 20 may be a diesel-powered engine, agasoline-powered engine, alternate-fuel-powered engine, or hybrid. Theengine 20 generates power by combusting a fuel and air mixture withincombustion chambers housed by the engine. The combustion of the mixturedrives linearly-actuated or rotary-type pistons. The linear orrotational motion of the pistons rotates an engine output shaft thattransfers power to a drivetrain (e.g., transmission) of a vehicle tomove the vehicle. The amount of power generated by the engine 20 islargely dependent upon the quantity and timing of fuel added or injectedinto the combustion chambers. For example, the more fuel added to andcombusted in the combustion chambers, generally the higher the powergenerated and fuel consumed by the engine. The quantity and timing offuel added to the combustion chambers is dependent upon a variety ofoperating conditions, such as engine speed, engine load (e.g., demand),vehicle speed, air intake characteristics, pressure, and temperature.

Generally, fuel injection quantity and timing values are obtained fromat least one predetermined control surface that relates fuel injectionquantity and timing values to engine operating conditions. For example,in one basic implementation, the control surface specifies fuelinjection quantity and timing values as a function of engine speed andengine load demand values. Accordingly, in such an implementation, thefuel quantity to be added to the combustion chambers is the fuelquantity value corresponding to the current engine speed and desired orrequired engine load. In other implementations, in addition to theengine speed and engine load values, the control surface also accountsfor one or more additional current operating condition values, such asvehicle speed, current air intake characteristics (e.g., air intake massflow, intake mass concentration, etc.), current pressure (e.g., airintake pressure, ambient air pressure, exhaust pressure, etc.), andcurrent temperature (e.g., air intake temperature, ambient airtemperature, exhaust temperature, etc.). Accordingly, in such otherimplementations, the fuel quantity to be added to the combustionchambers is the fuel quantity value corresponding with the currentengine speed and desired engine load, and the one or more additionaloperating condition values at the current engine speed and desiredengine load.

The control surface or surfaces for an internal combustion engine of avehicle are typically stored in the vehicle's electronic control module(ECM) or controller. In the illustrated embodiment, the controller 30 ofthe system 10 stores at least one control surface (see, e.g., FIG. 3).The controller 30 communicates with and/or receives communication fromvarious components of the system 10, including the engine 20, anaccelerator pedal 40, a clutch 50, one or more virtual or physicalsensors 60, and other possible components, such as on-board diagnosticsystems. Generally, the controller 30 controls the operation of theengine system 10 and associated sub-systems, such as the engine 20. Thecontroller 30 is depicted in FIG. 1 as a single physical unit, but caninclude two or more physically separated units or components in someembodiments if desired.

In certain embodiments, the controller 30 receives multiple inputs,processes the inputs, and transmits multiple outputs. The multipleinputs may include sensed measurements from the sensors and various userinputs. In one implementation, the inputs include engine speed, desiredengine load, vehicle speed, intake air characteristics, air and exhaustpressure, air and exhaust temperatures, and the like. The inputs areprocessed by the controller 30 using various algorithms, stored data,and other inputs to update the stored data and/or generate outputvalues. The generated output values and/or commands are transmitted toother components of the controller and/or to one or more elements of theengine system 10 to control the system to achieve desired results, andmore specifically, achieve desired fuel consumption characteristics.

The controller 30 includes various modules and stores information forcontrolling the operation of the engine system 10. For example, as shownin FIGS. 2 and 3, the controller 30 includes a conditions module 100, apermission module 110, and an engine command module 120. Additionally,the controller 30 includes a torque-speed curve and associated controlsurface or surfaces 200 that form part of the engine command module 120.Generally, the modules 100, 110, 120 and torque-speed curve and controlsurfaces 200 of the controller 30 cooperate to generate one or moreengine commands 150 requesting one or more operating conditions of theengine, such as those associated with the fuel efficiency of the enginesystem 10 (e.g., quantity of fuel to be injected, timing of the fuelinjection, etc.).

The accelerator pedal 40 of the engine system 10 receives throttle inputfrom a driver of the vehicle in which the engine system is housed, andcommunicates the throttle input to the controller 30 via an enginetorque demand 160. The throttle input is received from the driver viathe driver's positioning of the accelerator pedal 40, which can be afoot pedal, hand pedal, or other type of acceleration input device. Insome implementations, such as during certain operating modes, thedesired engine load is at least partially based on the throttle input.However, in other operating modes, such as during activation of cruisecontrol, the desired engine load is determined independently of thethrottle input.

For unthrottled engines, such as traditional diesel engines, theposition of the accelerator pedal 40 of the vehicle may be proportionalto the fuel quantity injected into the engine, as well as the operationof one or more actuators that indirectly influence the amount of freshair being introduced into the engine. In certain implementations, thedriver-controlled position of the accelerator pedal 40 is utilized bythe controller 30 to generate the engine command 150 for the engine 20.

The clutch 50 is a transmission clutch that is selectively used todecouple an engine output shaft (e.g., crankshaft) from a transmissioninput shaft of a transmission system (not shown). Generally, the clutch50 is actuated to disengage the transmission input shaft from the engineoutput shaft. Therefore, when the clutch 50 is not actuated, the engineoutput shaft and transmission input shaft are engaged. Accordingly, theclutch 50 is selectively operable between a disengaged configuration inwhich the clutch allows rotational engagement between the engine outputshaft and transmission input shaft, and an engaged configuration inwhich the clutch rotationally disengages (e.g., physically separates)the engine output shaft and the transmission input shaft. Rotationalengagement between the engine output shaft and transmission input shaftmeans the transmission input shaft co-rotates with (e.g., is rotated by)the engine output shaft. Rotational disengagement between the engineoutput shaft and transmission input shaft means the transmission inputshaft rotates independent of the engine output shaft. In other words,when rotationally disengaged from the engine output shaft, thetransmission input shaft slips relative to the engine output shaft. Thetransmission can be a manual transmission such that the clutch 50 ismanually operated by an operator of the vehicle. In contrast, thetransmission can be an automated transmission such that the clutch isautomatically operated pursuant to a gear ratio adjustment scheme. Insome implementations, an engine system 10 is equipped to selectivelyswitch between manually-operated and automatically-operated modes.

An out-of-gear condition is created when the clutch 50 is operating inthe actuated condition. In other words, the engine system 10 isconsidered to be out-of-gear when the engine output shaft and thetransmission input shaft are decoupled. Accordingly, the engine system10 can be placed into the out-of-gear position by operating the clutch50 in the actuated condition. For example, in the case of amanually-operated transmission, the engine system 10 can be operatedout-of-gear by actuating a manually-operated clutch pedal, paddle,button, shifter, or other actuation device. Likewise, for amanually-operated transmission, the engine system 10 can be operatedin-gear by releasing or deactivating the manually-operated clutch. Forautomated transmissions, in some embodiments, the engine system 10 isautomatically operated in the out-of-gear condition by electronicallyactuating a clutch during preprogrammed transitions from one gear ratioto another gear ratio.

Alternatively, the transmission input shaft and engine output shaft canbe decoupled without the use of the clutch pedal or without a controlmodule of an automatic or automated manual transmission actuating theclutch during an operation known commonly as float shifting. Floatshifting is executed by the vehicle operator or control module (in thecase of an automated shifting transmission) by taking the transmissionout of gear during a no-load event (e.g., as the torque being generatedby the engine passes from positive to negative, or negative topositive). During a no-load event, the lack of load on the transmissiongears enables a shift out of gear with very low force on the shiftingmechanism.

The sensors 60 include one or more sensing devices configured to sense(e.g., detect, measure, etc.) at least one operating condition andreport the sensed operating condition to the controller 30. In someembodiments, the sensors 60 include one or more of intake air mass flowsensors, pressure sensors, temperature sensors, engine speed sensors,vehicle speed sensors, exhaust mass concentration sensors, clutchposition sensor, out-of-gear conditions sensors, and the like. Forexample, in one illustrated implementation, one or more of the sensors60 is an engine speed sensor that reports a sensed engine speed 130 tothe controller 30. Moreover, in one illustrated implementation, one ormore of the sensors 60 is a clutch position sensor that reports a sensedclutch position 140 or configuration to the controller 30.Alternatively, or additionally, the sensors 60 can be out-of-gearcondition sensors that report various sensed out-of-gear conditions 145to the controller 30. The sensors 60 can include physical sensors and/orvirtual sensors. Moreover, the sensors 60 can include any of variousother sensors for detecting operating conditions that may be indirectlyassociated with the engine speed and out-of-gear condition, but fromwhich a determination of the engine speed and out-of-gear condition canbe obtained.

The conditions module 100 of the controller 30 is configured to receivesensed operating conditions of the system 10, convert the sensedoperating conditions into useable operating condition data if necessary,and forward the operating condition data to the permission module 110.In the illustrated embodiment, the conditions module 100 receives acurrent engine speed 130 and clutch position 140 from correspondingsensors 60. The conditions module 100 transmits the current engine speed130 directly to the permission module 110. However, the conditionsmodule 100 may convert the sensed clutch position 140 into one of anin-gear or out-of-gear condition. For example, if the sensed clutchposition 140 is deactivated as described above, then the conditionsmodule 100 transmits operating condition data indicating an in-gearcondition of the system to the permission module 110. However, if thesensed clutch position 140 is actuated as described above, then theconditions module 100 transmits operating condition data indicating anout-of-gear condition of the system to the permission module 110.

In some implementations, the conditions module 100 receives any ofvarious out-of-gear conditions 145 from one or more correspondingout-of-gear sensors. In one implementation, the out-of-gear sensors mayinclude a transmission input shaft speed sensor configured to detect thespeed of the transmission input shaft. In such an implementation, theconditions module 100 compares the detected engine speed 130 (e.g., thespeed of the engine output shaft) with the detected transmission inputshaft. The conditions module 100 is configured to transmit operatingcondition data indicating an in-gear condition if the engine outputshaft speed is the same as the transmission input shaft speed.Alternatively, the conditions module 100 transmits operating dataindicating an out-of-gear condition if the detected engine output shaftspeed and transmission input shaft speed are different.

According to another implementation, the out-of-gear sensors may includea transmission output shaft (e.g., tail shaft) speed sensor configuredto detect the speed of the transmission output shaft. The conditionsmodule 100 compares the detected engine speed 130, or engine outputshaft speed, and the detected transmission output shaft speed todetermine a transmission gear ratio. In some implementations, thetransmission output shaft speed can be determined based on a vehicle'sspeed, fixed rear axle ratio, and tire diameter. The transmission gearratio is the ratio of the engine output shaft speed to the transmissionoutput shaft speed. The conditions module 100 then compares thedetermined or actual transmission gear ratio to an expected orpredetermined transmission gear ratio for in-gear conditions. Theexpected transmission gear ratio is a known or predetermined value basedon the selected transmission gear. Basically, the engine output shaftand transmission output shaft will rotate at one of several discretetransmission gear ratios relative to each other whenever thetransmission is in gear and the clutch is not activated. If the actualtransmission gear ratio is different than the expected transmission gearratio, then the conditions module 100 is configured to transmitoperating condition data indicating an out-of-gear condition (e.g.,because clutch is activated or transmission is in neutral). In contrast,if the actual transmission gear ratio is approximately the same as theexpected transmission gear ratio, then the conditions module 100 isconfigured to transmit operating condition data indicating an in-gearcondition.

The permission module 110 compares the operating condition data receivedfrom the conditions module 100 to predetermined threshold conditions.Based on the comparison, the permission module 110 determines whetheraccess to a high engine speed region 250 of a torque-speed curve andassociated control surface 200 is allowed (see, e.g., FIG. 3).

In embodiments that facilitate high speed downshifting events, thepermission module 110 compares the current engine speed 130 to a maximumdownshift speed or downshift speed limit 260 (see, e.g., FIG. 3). Themaximum downshift speed 260 is defined as the maximum engine speed thata downshift out of top gear can occur. More specifically, the maximumdownshift speed 260 is set to prevent a downshift at engine speeds abovethe maximum downshift speed. If the current engine speed 130 is abovethe maximum downshift speed 260, then the permission module 110 may makea high engine speed region accessible for a downshift event. Otherwise,the permission module 110 denies access to the high engine speed regionif the speed 130 is below the maximum downshift speed.

The maximum downshift speed 260 is dependent upon the governed speed ofthe engine. Basically, the governed engine speed is the maximum enginespeed at which full torque can be achieved. For purposes of thisdisclosure, full torque is defined as any torque above the torquerequired to accommodate accessory loads placed on the engine. As shownin FIG. 3, the governed engine speed can be defined as the engine speedat which the torque-speed curve 210 intersects an accessory power curve220. The accessory power curve 220 represents the constant powerconsumed by accessories powered by the engine during normal operation.The accessories can include any of various accessories commonly used inthe art, such as a cooling fan, air pump, air compressor, alternator,air-conditioning pump, and the like. In one implementation, the constantpower of the power curve 220 is about 170 HP for “fan-on” operation.However, the constant power of the curve 220 can vary based on engineconfiguration type and the power consumption levels of the accessories.Accordingly, the maximum governed speed can vary during operation of theengine based on variations in the constant power curve 220. Generally,the engine is operating under a no-load operating condition when theload generated by the engine is not more than the engine load associatedwith the power curve 220.

Generally, beyond the governed engine speed, the torque output of theengine rapidly decreases. For example, for an isochronous governor, thetorque immediately drops to zero after the governed engine speed, andfor droop type governors, the torque rapidly drops to zero after thegoverned engine speed. As shown in FIG. 3, for isochronous torque-speedcurves (see, e.g., torque-speed curve 210), the governed engine speed isthe speed associated with immediate drop of the torque-speed curve 210,which is defined as the maximum full-load speed portion 215 of the curve210 (see, e.g., FIG. 3). Although an engine may be physically capable ofachieving engine speeds above the governed engine speed, the controller30, and more specifically, the torque-speed curve and associated controlsurface 200, limits the maximum engine speed at which full torque isachieved to the governed engine speed.

The governed speed of the engine, which is dependent on the torque-speedcurve as discussed above, can be set based on various factors. In someimplementations, one factor affecting the governed engine speed is thedesired fuel efficiency or engine brake performance of the engine.Generally, operating an engine at higher engine speeds tends to degradethe fuel efficiency of an engine. Correspondingly, operating the engineat lower or medium engine speeds tends to improve the fuel efficiency ofthe engine. Accordingly, reducing the governed engine speed can resultin an overall improvement in the fuel efficiency of an engine bypreventing operation of the engine at fuel-efficiency-reducing higherspeeds. In one specific implementation, the governed engine speed isreduced from a higher governed engine speed, which is associated withthe maximum full-load speed portion 235 (e.g., 2,100 RPM), to the lowergoverned engine speed, which is associated with the maximum full-loadspeed portion 215 (e.g., 1,800 RPM). The reduction of the governedengine speed results in an improvement in the fuel efficiency of theengine.

However, one consequence of reducing the governed engine speed is acorresponding reduction in downshift capability. In other words,reducing the governed engine speed limits the engine speed range inwhich a downshift event can occur. Basically, if the engine speed changeassociated with a desired transmission gear ratio change would result inan engine speed above the governed engine speed, a downshift even cannotbe successfully executed.

Access to engine speeds above the governed engine speed during a“no-load” out-of-gear condition does not substantially negatively affectthe fuel efficiency of the engine. Accordingly, granting permission toaccess an operating region (e.g., high engine speed operating region250) with engine speeds above the governed engine speed allows greaterrange for executing downshift events while preserving the fuelefficiency benefits associated with reducing the governed engine speed.

In the illustrated embodiment, the permission module 110 grants ordenies access to the high engine speed region based on whether theengine system 10 is operating in an out-of-gear condition as determinedby the conditions module 100. The permission module 110 may grantpermission to access the high engine speed operating region 250 when theout-of-gear condition is met. However, the permission module 110 deniespermission to access the high engine speed operating region 250 when theout-of-gear condition is not met (i.e., the engine system 10 isoperating in an in-gear condition).

The granting or denial of permission to the high engine speed region 250by the permission module 110 is communicated to the engine commandmodule 120. As shown in FIG. 3, the engine command module 120 includes acombined torque-speed curve and associated control surface 200. As usedherein, a torque-speed curve defines the electronically imposed enginespeed and torque limits that are calibrated into the controller 30. Thetorque-speed curve is independent of any engine operation commands(e.g., fuel injection, air handling, etc.). Essentially, thetorque-speed curve limits the quantity of fuel that can be injected intoan engine as a function of engine speed. In contrast, a control surface,as used herein, is where specific engine operation commands are stored.Although other operation commands are possible (e.g., fresh air flow,actuator positions, etc.), in some embodiments, the control surfacecontains multiple fuel pulse quantity and timing commands, in additionto charge flow and EGR fraction commands. In certain implementations,multiple control surfaces with pre-calibrated engine operation commandsmay be used based any number of inputs to the controller 30. Althoughoccupying different parts of fuel efficiency calibration, thetorque-speed curve (by virtue of torque limiting) and the controlsurface(s) (by virtue of combustion and pumping efficiency) impact fuelefficiency.

The torque-speed curve and associated control surface 200 includes astandard operating region 240 defined under the torque-speed curve 210,which includes the maximum full-load speed portion 215 that defines thegoverned engine speed. Further, the torque-speed curve and associatedcontrol surface 200 includes the high engine speed operating region 250defined between the maximum full-load speed portion 215 of thetorque-speed curve 210, the maximum full-load speed portion 235associated with a conventional torque-speed curve 230 (which has ahigher governed engine speed and higher intermediate engine speeds forthe same torque values), and the power curve 220. Because the maximumtorque or power of the engine 20 allowed during operation within thehigh engine speed operating region 250 is limited to the power curve220, which corresponds with the minimum power necessary to operateaccessories powered by the engine, not only is improved fuel efficiencymaintained, but a disincentive to tamper with or override the controller30 to extract additional fuel and power is created.

The torque-speed curve and associated control surface 200 includespredetermined fuel quantities (and/or fuel injection timing parameters,air handling parameters, EGR parameters, or other operating parameters)for various torque-speed combinations within the standard operatingregion 240 and high engine speed operating region 250. Generally, thepredetermined fuel quantities, and/or other predetermined parametervalues populating the torque-speed curve and associated control surface200 are selected to produce a desired fuel economy in view of otherconsiderations, such as performance, power, operator inputs, etc.

The engine command module 120 receives one or more engine torque demands160, such as a throttle input, accessory power demands, and the like,and the current engine speed 130. The engine torque demands 160 andengine speed 130 are compared against the torque-speed curve andassociated control surface 200 to determine the desired operatingparameters (e.g., fuel quantity) for achieving the engine torque demandsat the given engine speed. The engine command module 120 then generatesone or more engine commands 150 (e.g., fuel injection commands) forachieving the desired operating parameters.

The engine command module 120 also receives the permission status of thehigh engine speed region 250 from the permission module 110. Based onthe permission status, the engine command module 120 either allowsaccess to the high engine speed operating region 250 or disallows accessto the high engine speed operating region. For example, if thepermission module 110 grants access to the high engine speed operatingregion 250, the engine system 10 may perform a downshift event thatrequires the speed of the engine to be increased above the governedengine speed. In one implementation, following the downshift event, thespeed of the engine may remain above the governed engine speed. However,no additional fueling above the amount of fuel necessary for meeting theconstant power associated with the power curve 220 is allowed until thespeed of the engine is reduced to the governed engine speed or lower.Because no additional fueling is allowed during operation in the highengine speed operation region 250, the increase in engine speedassociated with operation in the high engine speed region does notnegatively impact the fuel efficiency of the engine system 10.

Referring to FIG. 4, one embodiment of a method 300 for controllingoperation of the engine 20 may be executed by the one or more of themodules described above. According to one implementation, the method 300begins by determining the speed of the engine 20 at 310. The method 300then determines whether the engine speed is less than a maximumdownshift speed at 320. If the engine speed is less than the maximumdownshift speed, then the method 300 prevents access to a high enginespeed operating region (e.g., region 250) and again determines theengine speed at 310. However, if the engine speed is more than themaximum downshift speed, then the method 300 proceeds to determine if anout-of-gear condition has been met at 330. In other implementations ofthe method 300, the steps 310, 320 are not performed, and the methodproceeds directly to step 330 after starting.

If the out-of-gear condition has been met (e.g., the clutch 50 isengaged, relative rotation between engine output shaft and transmissioninput shaft is detected, the engine operating load is not greater thanthe load associated with the accessory power curve 220 (e.g., floatshifting event occurring), and/or other operation conditions arepresent), then the method 300 allows access to a high engine speedoperating region at 335 and the method ends. But, if the out-of-gearcondition has not been met or an in-gear condition is met (e.g., theclutch 50 is not engaged, co-rotation between engine output shaft andtransmission input shaft is detected, and/or other operation conditionsare present), then the method 300 prevents access to a high engine speedoperating region and again determines the engine speed at 310.

In addition to allowing limited access to high engine speeds fordownshift events and improving the fuel efficiency of the engine system10, reducing the governed engine speed also facilitates the use of moreefficient turbochargers with the system. Because the engine speedsassociated with standard operation of the engine system 10 are lowercompared to conventional systems, more efficient turbochargersconfigured for operation at lower speeds can be utilized with less fearof negative side effects (e.g., turbo choke) associated with high enginespeeds.

The schematic flow chart diagrams and method schematic diagramsdescribed above are generally set forth as logical flow chart diagrams.As such, the depicted order and labeled steps are indicative ofrepresentative embodiments. Other steps, orderings and methods may beconceived that are equivalent in function, logic, or effect to one ormore steps, or portions thereof, of the methods illustrated in theschematic diagrams.

Additionally, the format and symbols employed are provided to explainthe logical steps of the schematic diagrams and are understood not tolimit the scope of the methods illustrated by the diagrams. Althoughvarious arrow types and line types may be employed in the schematicdiagrams, they are understood not to limit the scope of thecorresponding methods. Indeed, some arrows or other connectors may beused to indicate only the logical flow of a method. For instance, anarrow may indicate a waiting or monitoring period of unspecifiedduration between enumerated steps of a depicted method. Additionally,the order in which a particular method occurs may or may not strictlyadhere to the order of the corresponding steps shown.

Many of the functional units described in this specification have beenlabeled as modules, in order to more particularly emphasize theirimplementation independence. For example, a module may be implemented asa hardware circuit comprising custom VLSI circuits or gate arrays,off-the-shelf semiconductors such as logic chips, transistors, or otherdiscrete components. A module may also be implemented in programmablehardware devices such as field programmable gate arrays, programmablearray logic, programmable logic devices or the like.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions, which may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the module and achieve the stated purposefor the module.

Indeed, a module of computer readable program code may be a singleinstruction, or many instructions, and may even be distributed overseveral different code segments, among different programs, and acrossseveral memory devices. Similarly, operational data may be identifiedand illustrated herein within modules, and may be embodied in anysuitable form and organized within any suitable type of data structure.The operational data may be collected as a single data set, or may bedistributed over different locations including over different storagedevices, and may exist, at least partially, merely as electronic signalson a system or network. Where a module or portions of a module areimplemented in software, the computer readable program code may bestored and/or propagated on in one or more computer readable medium(s).

The computer readable medium may be a tangible computer readable storagemedium storing the computer readable program code. The computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, holographic,micromechanical, or semiconductor system, apparatus, or device, or anysuitable combination of the foregoing.

More specific examples of the computer readable medium may include butare not limited to a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), a portable compact discread-only memory (CD-ROM), a digital versatile disc (DVD), an opticalstorage device, a magnetic storage device, a holographic storage medium,a micromechanical storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, and/or storecomputer readable program code for use by and/or in connection with aninstruction execution system, apparatus, or device.

The computer readable medium may also be a computer readable signalmedium. A computer readable signal medium may include a propagated datasignal with computer readable program code embodied therein, forexample, in baseband or as part of a carrier wave. Such a propagatedsignal may take any of a variety of forms, including, but not limitedto, electrical, electro-magnetic, magnetic, optical, or any suitablecombination thereof. A computer readable signal medium may be anycomputer readable medium that is not a computer readable storage mediumand that can communicate, propagate, or transport computer readableprogram code for use by or in connection with an instruction executionsystem, apparatus, or device. Computer readable program code embodied ona computer readable signal medium may be transmitted using anyappropriate medium, including but not limited to wireless, wireline,optical fiber cable, Radio Frequency (RF), or the like, or any suitablecombination of the foregoing

In one embodiment, the computer readable medium may comprise acombination of one or more computer readable storage mediums and one ormore computer readable signal mediums. For example, computer readableprogram code may be both propagated as an electro-magnetic signalthrough a fiber optic cable for execution by a processor and stored onRAM storage device for execution by the processor.

Computer readable program code for carrying out operations for aspectsof the present invention may be written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Java, Smalltalk, C++ or the like and conventionalprocedural programming languages, such as the “C” programming languageor similar programming languages. The computer readable program code mayexecute entirely on the user's computer, partly on the user's computer,as a stand-alone software package, partly on the user's computer andpartly on a remote computer or entirely on the remote computer orserver. In the latter scenario, the remote computer may be connected tothe user's computer through any type of network, including a local areanetwork (LAN) or a wide area network (WAN), or the connection may bemade to an external computer (for example, through the Internet using anInternet Service Provider).

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment. Similarly, the use of theterm “implementation” means an implementation having a particularfeature, structure, or characteristic described in connection with oneor more embodiments of the present disclosure, however, absent anexpress correlation to indicate otherwise, an implementation may beassociated with one or more embodiments.

The present disclosure may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the disclosure is, therefore,indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. An apparatus for controlling operation of aninternal combustion engine, comprising: a conditions module configuredto determine an out-of-gear condition of the internal combustion engine;and a permission module configured to allow a speed of the internalcombustion engine to exceed a maximum engine speed limit if thedetermined out-of-gear condition meets a threshold, and prevent thespeed of the internal combustion engine from exceeding the maximumengine speed limit if the determined out-of-gear condition does not meetthe threshold.
 2. The apparatus of claim 1, wherein the conditionsmodule determines the out-of-gear condition based on actuation of atransmission clutch.
 3. The apparatus of claim 1, wherein the conditionsmodule determines the out-of-gear condition based on a differencebetween the speed of the internal combustion engine and a speed of atransmission input shaft.
 4. The apparatus of claim 1, wherein theconditions module determines the out-of-gear condition based on adifference between an expected engine output and transmission outputshaft speed ratio and a detected engine output and transmission outputshaft speed ratio.
 5. The apparatus of claim 1, wherein the conditionsmodule determines the out-of-gear condition based on an electronicsignal from an automated transmission controller.
 6. The apparatus ofclaim 1, wherein the permission module is further configured to allowthe speed of the internal combustion engine to exceed the maximum enginespeed limit if the speed of the engine is above a downshift speed limit,and to prevent the speed of the internal combustion engine fromexceeding the maximum engine speed limit if the speed of the engine isbelow the downshift speed limit, wherein the downshift speed limit isless than the maximum engine speed limit.
 7. The apparatus of claim 1,wherein the permission module is further configured to allow the speedof the internal combustion engine to exceed the maximum engine speed ifthe engine is not operating above a minimum power threshold, and toprevent the speed of the internal combustion engine from exceeding themaximum engine speed if the engine is operating above the minimum powerthreshold.
 8. The apparatus of claim 7, wherein the minimum powerthreshold is equal to the power consumed by accessories powered by theengine.
 9. The apparatus of claim 1, wherein the maximum engine speed isa maximum full-load speed.
 10. The apparatus of claim 1, wherein thepermission module allows access to the high speed region to accommodatean engine speed change associated with a desired downshift event thatwould result in the engine speed exceeding the maximum engine speedlimit.
 11. An internal combustion engine system, comprising: an internalcombustion engine comprising an engine output shaft; a transmissionclutch configured to selectively couple the engine output shaft to atransmission input shaft and decouple the engine output shaft from thetransmission input shaft; and a controller comprising a predeterminedtorque-speed map defining a first operating region for engine speedsbelow a maximum engine speed and a second operating region for enginespeeds above the maximum engine speed, wherein operation of the internalcombustion engine within the second operating region is allowed onlywhen the transmission input shaft is selectively decoupled from theengine output shaft.
 12. The system of claim 11, further comprisingexternal accessories in power receiving communication with the internalcombustion engine, wherein operation of the internal combustion enginewithin the second operating region is allowed only when the transmissioninput shaft is selectively decoupled from the engine output shaft andwhen power generated by the internal combustion engine is not more thanthe power received by the external accessories from the internalcombustion engine.
 13. The system of claim 11, wherein operation of theinternal combustion engine within the second operating region is allowedonly when the transmission input shaft is selectively decoupled from theengine output shaft during a downshift event.
 14. The system of claim11, wherein the second operating region comprises an upper engine speedlimit equal to an engine speed required to downshift out of a top gearwhen the internal combustion engine is operating at the maximum enginespeed, the upper engine speed limit being greater than the maximumengine speed.
 15. The system of claim 11, wherein the second operationregion comprises a no-engine-load operating region.
 16. A method forcontrolling operation of an internal combustion engine system,comprising: determining whether the internal combustion engine system isout-of-gear; providing an engine operation map comprising a high speedregion; allowing access to the high speed region when the internalcombustion system is out-of-gear; and preventing access to the highspeed region when the internal combustion system is not out-of-gear. 17.The method of claim 16, further comprising determining an engine speedof the internal combustion engine system, allowing access to the highspeed region when the engine speed of the internal combustion enginesystem is greater than a maximum downshift speed, and preventing accessto the high speed region when the engine speed of the internalcombustion engine system is less than the maximum downshift speed. 18.The method of claim 16, further comprising determining a power output ofthe internal combustion engine system, allowing access to the high speedregion when the power output of the internal combustion engine system isnot greater than an external accessory power consumption, and preventingaccess to the high speed region when the power output of the internalcombustion engine system is more than the external accessory powerconsumption.
 19. The method of claim 16, wherein the high speed regioncomprises engine speeds greater than a maximum governed speed limit ofthe engine.
 20. The method of claim 16, wherein allowing access to thehigh speed region accommodates an engine speed change associated with adesired downshift event that would result in the engine speed exceedinga maximum governed speed limit of the engine.